Cathode-ray projection tube



Sept. 20, 1949. H. G. BOYLE CATHODE-RAY PROJECTION TUBE Filed Aug. 18, 1944 NN MN Patented Sept. 20, 1949 Homer G. Boyle,

of Delaware,

Application August 18,

" This-invention relates tocathode ray tubes, and

moreparticularly to-cathode ray projection systerns for use in television and the like.

'Anobject of thepresent invention is to provide a cathode ray tube incorporating a projection A system.

Another. object of the invention is to provide a cathoderay-projection tube having a higher light output than-existing. cathode ray projection systems.

Av further object of the invention is to combine acathode ray tubezand a projection system intoone integral unit soas: to permanently align one-With the other.

Still another object of the invention is to provide a cathode ray. projection tube with an accelerator ring forming partof the lens system.

.A-. still further object of the. invention is to providea cathode ray projection tube with an accelerator ring forming part of thegun structure.

Yet another objectgof the invention is to provide a cathode ray projection tube incorporating coolingmeans aspart of the integral projection tube structure.

Other objects, and the manner inlwhich the same are obtained-, will appear from the following description.

An outstanding problem in cathode ray projectlon is that of obtaining maximum light output; Closely interwoven with this are problems of electron acceleration, to impart suflicient energy to the electrons; of screen arrangmenhto obtain ,optimum'energy translation in the screen; of screen cooling, to avoid energy losses and shortening of-the life of the screen due to overheating, and of optical projection, to;minimi ze light losses during passage of the light rays through the optical-lens system. Past attempts ata. solution of the center problem have failed, it seems, for the reason that improvements of some of these factors were obtained to the detriment of the others, with the result that in-theend the main problem of obtaining maximum light output was hardly nearer to solution than before.

The present invention contemplates solving this problem, and thereby obtaining a light out-, put-severaltimes that heretofore obtainable, by providing a cathode ray tube incorporating a projection system as part of the integral tube structure, and similarly incorporating with this structureaccelerating and, if desired, also cooling means so that the whole forms a unified assembly.

A suitabIeembodiment of the invention is a cathode ray-projection tube includin in addition.

I toia standard type gun-structure designed for- Dobbs Ferny; N. Y., alssignor, by mcsne assignments, to Philips Ino., Irvington on Hudsom Laboratories, N. Y.,,a. corporation 1944, Serial'No. 550,077

12; Claims. (Cl: .250r-164) oustomary basingand assemblymethods, a bulbous envelope portion with a rear wall mounting a reflector surfaceand forming a spherical mirror, and asfrontwall mounting, in its center, a fluorescent-screenfacing the gun structure, Whilea corrector plate correcting-for the spherical aberration-of the mirror is arranged in the part of the front wall surrounding the screen-so mirror and plate combinetoactias-aSchmidt lens system of greatgatheringapower; high aperture and small focal ratio. According to a. preferred embodiment of the invention, the partofthefrontwall surrounding the screen, itself forms the 'corrector plate; ,as an alternative, this part'maymount a correctorplate preierablymade of: plastic. and in.- timately joined to this part so thatineither case, the Schmidt lens system forms part. of the integral cathode.;ray tube structure, according to the basic: concept of the; invention.

Two. accelerator rings are contemplated for post deflection l acceleration-- of theelectrons originate ing -inthe 'gun, one being mounted-on extensions of the;guns structural members extending into the bulbous envelope portion While for the other; according. to 'a;preferred embodiment of the invention, the;metallic-refiector surface on the rear Wallofthe bulbous envelope portion may be-;uti lized- As, an alternative, a second accelerator ring; maybe mounted on the gun structure in proximity-to the reflector surface.

The center of the front wall mounting the screen is dropped'relative to the plane of the surrounding part of the front wall forming or mounting thecorrector plateto provide tubes, and particularly tubes of; extremely high brilliance andpower with a cooling space for: the screen which thus is incorporated in the integral tube structure the same as are the; projection system and-theaccelerating rings.

Inthe, drawings affixed to this specification an forming part thereof several embodiments of the inventionare illustrated.diagrammatically by way of example.

Inthe drawings,

Fig. 1 is-a diagrammatic side view, with some parts shown in perspective, and others broken awayfor clarity, ofacathode rayproj-ection tube being. apreferred embodiment of the invention; Fig. 2 is, a -Simi18.lzShOWing of amodification of adetail ofv Fig. 1; I

Fig. 3 is a similar showing vofa modification of anotherdetailofl lig. 1; and

Fig-. -shows:a:.modification- .ofstill another :dee

Referring now to the drawing wherein like elements are denoted by identical reference numera,4s2,1ti

als, and first to Fig. 1, the cathode ray projection 7 tube according to the invention is seen to include a base I, a gun structure 2 and an envelope generally indicated at 3 and comprising a neck 4 and a bulbous portion 5.

The bulbousenvelope 6 with an opening 1 surrounded by a flange 8 by which portion is joined portion 5 has a rear wall to the neck 4. The rear wall 6 is so shaped and so coated with a metallic coating 9 of silver or aluminum, for example, as to form a spherical mirror generally indicated at H), the coating being disposed on thatside of the rear wall facingthe interior of bulbous portion 5 also has a front wall generally indicated at H and including the portion 5. The

a dropped center "nification' is obtained over comparatively short Ill and passed on to the corrector plate l5 or l5 through which they leave the tube.

The present invention results in numerous advantages. Not only is the fluorescent screen a Schmidt lens system of great gathering power,

I high aperture, and small focal ratio which is inherentlya wide angle lens system so large magprojection distances; 'but moreover, light losses I toa minimum by the elimination of glass surfaces and air space between surfaces. According to the preferred embodiment of the invention, there isno glass bulb in the light path portion l2 mounting a fluorescent screen l3 and defining a cavity 14 open toward the outside'and' servin as a cooling space; a marginal portion l5 formed as a corrector plate to correct for the envelope 5 and mount a corrector plate 15' pref erably made of plastic and intimately joined to part 5' so as to be part of the integral tube structure. V

' As an alternative to the ultilization of therereflector surface 9, and connected through a wire 24 to high voltage connector 22 on neck 4.

In tubes of extremely high brilliance and power, it is advisable to cool the screen by water cooling, for example, to avoid overheating and consequent shortenin of the life of the screen and reduction in the light output thereof. Fig. 4

cooling medium which is supplied through inlet 25 and discharged through outlet 26, a cover 21 closing the space H to seal the cooling chamber.

7 In the operation of the invention, a beam of electrons generated and deflected in the electron conventional practice, is accelerated either by reflector surface .9 acting as accelerator ring (Fig. l) or the individual accelerator ring 23 (Fig. 3) and further accelerated by accelerator ring l8, toimpinge on the target or fluorescent screen l3 where its energy is translated into visible intensity. The light raysthus generated are reflected by the coating 9, nowacting as reflector surface, of the spherical mirror tube structure.

to cause refraction: and attendant light losses,'

and even where, as in the modification of Fig. 2, a single glass portion in the light path is retained in return for maximum economy of manufacture, the sacrifice in light output is held to a minimum. The light rays leaving the screen travel in vacuo where-they are not subject to leave the tube and enter air In this manner,

that the light rays in substantially straight lines. I

a light output several times that of the most ad vanced cathode ray projection systems is ob tained. 2' The incorporation of the projection system in the cathode ray tube to'form an integral unit,

such as gun and screen, and the eeonomy of utilizing the mirror for the rear wall, and the screen for part of thefront wall of the bulbous tube portion. Other major advantages include the combination of accelerating rings with the lenssysand the incorporation of coolscreen as part of the integral unify the assembly; in means for the I wish it to be understood that I'do not desire to be limited to the exact details of construction, design and operation shown and described as various modifications within the scope of the appended claims may occur to a person skilled in theart. 1 1

Iclaim:

e '1. A cathode ray projection tube comprisingan rector plate for spherical aberration, said corrector' plate surrounding said screen and forming part of the front wall-of said portion. 1 Y I 2. A cathode ray projection tube comprising an electron gun, a bulbous envelope portion, a spherical mirror forming the rear wall of said portion;

for spherical aberration surrounding said scr'een;

3. A cathode ray projection ,tube' comprising an electron gun, a bulbous envelope portion, a rear wall in said portion forming a spherical mlrror, and a front wall in said ortion comprising a mountinga fluorescent screen inside said portion and defining a cavity on portion. g

, r 4. A cathode ray projectiontubecomprisingian the outside of said I rear wall in said portion forming a spherical mirror, and a front wall in said portion comprising a marginal part including a corrector plate for spherical aberration, a dropped center part mounting a fluorescent screen inside said portion and defining a cavity on the outside of said portion, and cooling means extending into said cavity.

6. A cathode ray projection tube comprising an electron gun, a bulbous envelope portion, a rear wall in said portion forming a spherical mirror, and a front wall in said portion comprising a marginal part including a corrector plate aberration, a dropped center part mounting a and defining a cavity on the outside of said portion, a cover sealing said cavity and coolin means extending through said cover into said cavity,

'7. A cathode ray projection tube having an envelope comprising a neck and a bulbous portion, a spherical mirror forming the rear wall, and a fluorescent screen and a corrector plate for spherical aberration surrounding said screen, in the front wall of said bulbous portion, an electron gun including structural members in said 1 neck, extensions mounted on said structural members and extending into said, bulbous portion, and an accelerator ring mounted on said extensions.

8. A cathode ray projection tube having an envelope comprising a neck and a bulbous portion, a spherical mirror having a metallic coating and forming the rear wall, and a fluorescent screen and a corrector plate for spherical aberration surrounding said screen, in the front wall of said bulbous portion, an electron gun including structural members in said neck, extensions mounted on said structural members and extending into said bulbous portion, an accelerator ring mounted on said extensions, and a high voltage connection leading to said coating to adapt the same for use as an additional accelerator ring.

9. A cathode ray projection tube having an envelope comprising a neck and a bulbous portion, a spherical mirror forming the rear wall, and a fluorescent screen and a corrector plate for spherical aberration surrounding said screen, in the front wall of said bulbous portion, an electron gun including structural members in said neck, extensions mounted on said structural members and extending into said bulbous portion, an accelerator ring mounted on the ends of said extensions, and an additional accelerator ring mounted on said extensions in proximity to said mirror.

10. A cathode ray projection tube having an envelope comprising a neck and a bulbous portion, an electron gun in said neck portion, a spherical mirror forming the rear wall of said bulbous portion, and a fluorescent screen and a corrector plate for spherical aberration surrounding said screen forming the front wall of said bulbous portion.

11. A cathode ray projection tube comprising a neck portion and a bulbous envelope portion, a rear wall in said bulbous portion having a shape and a metallic coating such as to form a spherical mirror, a high voltage connection leading to said coating, a fluorescent screen in said bulbous portion and spaced from said coating, an accelerator ring within said bulbous portion between said fiuorescent screen and said coating, and a high voltage connection leading to said ring.

12. A cathode ray projection tube comprising a neck portion and a bulbous envelope portion, an electron gun including structural members in said neck portion, a rear wall in said bulbous portion having a shape and a metallic coating such as to form a spherical mirror, 9. high voltage connection leading to said coating, a fluorescent screen in said bulbous portion and spaced from said coating, extensions mounted on said structural members, and an accelerator ring mounted on said extensions.

HOMER G. BOYLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,049,781 Schlesinger Aug. 4, 1936 2,053,537 Schlesinger Sept. 8, 1936 2,166,399 Dowsett et a1 July 18, 1939 2,283,041 Broadway May 12, 1942 2,292,979 Wald Aug. 11, 1942 2,295,779 Epstein Sept. 15, 1942 2,298,808 Ramberg Oct. 13, 1942 2,305,855 Epstein et al Dec. 22, 1942 2,440,735 Cawein May 4, 1948 FOREIGN PATENTS Number Country Date 487,241 Great Britain June 16, 1938 557,771 Great Britain Dec. 3, 1943 

